Axial flow gas turbine engines generally include a compression section, a combustion section and a turbine section. A flow path for hot working medium gases extends axially through the sections of the engine. The gases are compressed in the compression section, burned with fuel in the combustion section and expanded through the turbine section to produce useful work.
A rotor assembly in the turbine section is used to extract useful work from the hot, pressurized gases. The rotor assembly includes a disk and a plurality of rotor blades which extend outwardly across the working medium flow path. The rotor blades, bathed in the hot working medium gases, are cooled to prevent overheating.
One example of a coolable rotor assembly is shown in commonly owned U.S. Pat. No. 4,279,572 issued to Auriemma entitled "Sideplates For Rotor Disk and Rotor Blades". The rotor assembly shown in Auriemma includes a rotor disk having a plurality of circumferentially spaced blade attachment slots. A rotor blade at each slot has a root spaced radially from the disk leaving a cavity therebetween. Cooling air is ducted from a source of supply via passages 50 to the cavity in the blade attachment slot. The cavity provides a plenum to supply cooling air to the coolable blade. Cooling air is flowed from the cavity either directly to the blade or through an orifice plate which meters the flow of cooling air from the cavity to the blade.
The cooling air is pressurized to an extent that enables the air to flow from the cavity through the rotor blade and thence to the high pressure environment of the working medium flow path. One source of pressurized cooling air is the compression section of the engine. As the working gases are passed through the compressor section, a portion of the pressurized gases (air) is bled from the working medium flow path. The pressurized air is ducted through the engine to a region adjacent to the disk. Because the cooling air is removed from the working medium flow path after energy is expended by the engine to pressurize the gases, the ineffective use or loss of pressurized air decreases the efficiency of the engine.
Accordingly, scientists and engineers are searching for ways to decrease the need for pressurized cooling air by finding and blocking cooling air leak paths to avoid waste of the cooling air. Of particular interest is the loss of cooling air from the cavity in the blade attachment slot through leak paths which extend between the rotor blade and the rotor disk.